Carbamate derivatives of the oxime of 1,2,5,6-tetrahydropyridin-3-carboxaldehyde, their use as medicaments and compositions containing them

ABSTRACT

Compounds useful in the treatment of patients suffering from senile dementia, Alzheimer&#39;s disease, or memory defects, of the formula &lt;IMAGE&gt; (I)  in which R&#39; represents hydrogen, a linear, branched or cyclic alkyl, alkenyl or alkynyl, containing up to 8 carbon atoms, and R represents a linear, branched or cyclic alkyl, alkenyl, or alkynyl, containing up to 18 carbon atoms, possibly substituted, aryl containing up to 14 carbon atoms, possibly substituted, aralkyl containing up to 18 carbon atoms, possibly substituted, as well as their addition salts with organic or mineral acids.

The present invention relates to new derivatives of the oxime of 1,2,5,6-tetrahydropyridin-3-carboxaldehyde, the process for their preparation, their use as medicaments and compositions containing them.

The subject of the invention is the compounds of the formula (I): ##STR2## in which R' represents hydrogen, a linear, branched or cyclic alkyl, alkenyl or alkynyl, containing up to 8 carbon atoms, and R represents a linear, branched or cyclic alkyl, alkenyl or alkynyl, containing up to 18 carbon atoms, possibly substituted, aryl containing up to 14 carbon atoms, possibly substituted, aralkyl containing up to 18 carbon atoms, possibly substituted, atoms, as well as their addition salts with organic or mineral acids.

Among the addition salts with acids, there can be cited those formed with mineral acids, such as hydrochloric, hydrobromic, sulphuric or phosphoric acids, or with organic acids such as formic, acetic, propionic, benzoic, maleic, fumaric, succinic, tartaric, citric, oxalic, glyoxylic, aspartic, alkanesulphonic, such as methane- or ethane-sulphonic, arylsulphonic such as benzene- or paratoluene-sulphonic acids.

When R represents linear or branched alkyl, it is preferred to be methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, n-pentyl, n-hexyl, tert-butyl, neopentyl or adamantyl.

When R' represents linear or branched alkyl, it is preferred to be methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, n-pentyl, tert-butyl, tert-pentyl, neopentyl or n-hexyl.

When R or R' represents alkenyl or alkynyl, it is preferred to be an ethylene radical such, for example, as vinyl, allyl, 1,1-dimethylallyl or but-2-enyl, or an acetylene radical such, for example, as ethynyl or propynyl.

When R or R' represents a cyclic alkyl radical, it is preferred to be cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cyclopropylmethyl, cyclobutylmethyl, cyclopentylmethyl or cyclohexylmethyl.

When R is a substituted alkyl, the substituent is prefered to be an alkylsulphonyl containing up to 18 carbon atoms or the radical Si--Alk₃ in which Alk represents an alkyl containing up to 4 carbon atoms.

When R represents aryl, it is preferred to be phenyl.

When R represents aralkyl, it is preferred to be phenalkyl, e.g., benzyl or phenethyl.

The aryl or aralkyl can include one or more substituents chosen from halogen such as chlorine or bromine, linear or branched alkyl such as methyl, ethyl, linear or branched propyl, linear or branched butyl, alkoxy such as methoxy, ethoxy, linear or branched propoxy, and linear or branched butoxy. When R represents an alkyl substituted with an alkylsulphonyl, it is preferred to be CH₂ SO₂ CH₃, --CH₂ CH₂ SO₂ CH₃, or --CH₂ CH₂ CH₂ SO₂ CH₃.

Among the preferred compounds of the invention, there can be cited the compounds in which R' represents linear alkyl, alkenyl or alkynyl containing up to 4 carbon atoms, such, for example, as methyl.

There can also be cited the compounds in which R represents linear alkyl, alkenyl or alkynyl, containing up to 4 carbon atoms, such, for example, as methyl, or also allyl or phenyl, a substituted phenyl such, for example as 4-chlorophenyl, isopropylphenyl or 3,4-dimethoxyphenyl, as well as their addition salts with mineral or organic acids.

As more preferred compounds of the invention, there can be cited the compounds described in examples 2, 4, 6, 12, 13 and 14 and more particularly the methyl ether of (4-chlorophenyloxy-carbonyl-1,2,5,6-tetrahydropyridin-3-carboxaldehyde oxime, as well as their addition salts with organic or mineral acids.

The products of the invention present very interesting pharmacological properties and notably an important cholinomimetic activity by oral route which has a long duration of action.

In addition, the products present a strong dissociation between the central activity and the peripheral activity as is shown by the results of the tests set our hereafter.

It is well known that difficulties of learning and of memory in elderly persons are connected above all with a defect of the central cholinergic system, in particular in senile dementia and Alzheimer's disease.

It is therefore evident that products having a central cholinergic action can be employed in therapeutic treatment of these maladies (Bartus, R. I. Science 217, 408, 1982).

It has been shown that arecoline injected by intravenous route has a positive effect on patients having a memory defect (Sitaram N. et al., Science 201, 274, 1978) (Christie J. E., et al., Brit. J. Psychiatry, 138, 46, 1981).

A limitation to the therapeutic use of arecoline is connected with the fact that this product has a very weak activity by oral route and a short duration of action.

The products which are the subject of the invention have shown, after administration by oral route, a central cholinomimetic activity very much greater than that of arecoline and with a longer duration of action.

Therefore the invention has as its subject the products as medicaments useful in particular in the treatment of Alzheimer's disease or senile dementia and also in the treatment of memory disorders.

More particularly, the subject of the invention, as medicaments, is the compounds of examples 2, 4, 6, 12, 13 and 14, as well as their addition salts with pharmaceutically acceptable acids.

The usual posology is variable according to the affection concerned, the subject treated and the administration route; it can be between 10 mg and 300 mg/day, preferably between 50 mg and 200 mg/day, for example, between 15 and 150 mg/day, preferably between 50 mg and 100 mg/day in one or more doses for the product of example 12 administered by oral route.

The present invention also has as its subject the pharmaceutical compositions according at least one product with the formula (I) as active principle.

The pharmaceutical compositions according to the invention can be solid or liquid, and are presented in the pharmaceutical forms currently used in human medicine, such, for example, as plain or sugar-coated tablets, capsules, granules, suppositories and injectable preparations; they are prepared according to the usual methods.

The active principle or principles can be incorporated in them with the excipients usually employed in these pharmaceutical compostions, such as talc, gum arabic, lactose, starch, magnesium stearate, cocoa butter, aqueous or non-aqueous vehicles, fatty substances of animal or vegetable origin, paraffin derivatives, glycols, the various wetting, dispersing or emulsifying agents and preservatives.

The invention also has as its subject a process for the preparation of the compounds with the formula (I) characterized in that a compound with the formula (II): ##STR3## in which R' retains the same significance as previously, is submitted to the action of an alkoxycarbonylation agent able to introduce the radical --CO₂ R, R being defined as previously, so as to obtain the corresponding compound with the formula (I), which, if desired, is submitted to the action of an acid in order to form its salt.

In a preferred way of carrying out the invention process, the alkoxycarbonylation agent is a product with the formula (III): ##STR4## in which X represents a halogen atom, a paranitrophenoxy radical or the radical ##STR5## R being defined as previously.

The invention also has as its subject a process characterized in that a compound with the formula (IV): ##STR6## in which R" represents a linear, branched or cyclic radical, saturated or unsaturated, containing up to 4 carbon atoms or an aralkyl containing up to 14 carbon atoms, is submitted to the action of an agent able to cleave the group R" and to introduce the group ##STR7## R being defined as previously, in order to obtain the corresponding compound with the formula (I): ##STR8## which, if desired, is submitted to the action of an acid to form its salt.

In a preferred way of realizing [the invention products] a compound is used with the formula (III): ##STR9## operating hot.

The starting products with the formulae (II) and (IV) are described and claimed in the European patent EP 0239445.

The following examples illustrate the invention, nevertheless without limiting it.

EXAMPLE 1 Methyl ether of 1-methoxycarbonyl-1,2,5,6-tetrahydropyridin-3-carboxaldehyde oxime

To a solution of 1.5 g of 1,2,5,6-tetrahydropyridin-3-carboxaldehyde-O-methyl oxime prepared as indicated in the patent application EP 239445, in 40 cm³ of benzene, 1.5 cm³ of triethylamine is added at 10° C., and, slowly, 0.83 cm³ of methyl chloroformate. After agitating for 30 minutes at ambient temperature, washing with 15 cm³ of 5% hydrochloric acid and then with water, evaporating to dryness under reduced pressure, then distilling the residue at 140° C. under 0.05 mbar, 1.91 g of the expected product is obtained. m.p. 37° C.

Analysis: C₉ H₁₄ N₂ O₃ Calculated: C% 54.53, H% 7.12, N% 14.13; Found: C% 54.31, H% 7.17, N% 14.00.

EXAMPLE 2 Methyl ether of 1-ethoxycarbonyl-1,2,5,6-tetrahydropyridin-3-carboxaldehyde oxime Method A

To a solution of 3.6 g of 1-benzyl-1,2,5,6-tetrahydropyridin-3-carboxaldehyde-O-methyloxime prepared as indicated in the patent application EP 239445, in 30 cm³ of dichloroethane, 2 cm³ of ethyl chloroformate is added, and the whole is kept at reflux for 3 hours. The reactive mixture is cooled and the organic phase is washed with 20 cm³ of hydrochloric acid at 5%, then twice with 25 cm³ of water. The solvent is evaporated, the residual oil is distilled at 150° C. under 0.05 mbar, and 1.5 g of the expected product is obtained.

Analysis: C₁₀ H₁₆ N₂ O₃ : Calculated: C% 56.59, H% 7.60, N% 13.20; Found: C% 56.82, H% 7.66, N% 13.04.

Method B

To a solution of 3.75 g of 1,2,5,6-tetrahydropyridin-3-carboxaldehyde-O-methyloxime prepared as indicated in the patent application EP 239445, in 60 cm³ of benzene, 3.75 cm³ of triethylamine and 2.7 cm³ of ethyl chloroformate are added at a temperature not exceeding 10° C. The mixture is agitated for 1 hour at ambient temperature, then 20 cm³ of water is added, followed by decanting, extracting with benzene, and evaporating to dryness under reduced pressure. The residue is chromatographed on silica (eluent: ethyl acetate-toluene, 1-1). The residue is distilled at 160°-165° C. under 0.07 mbar. 5.32 g of the expected product is obtained.

Analysis: C₁₀ H₁₆ N₂ O₃ Calculated: C% 56.59, H% 7.60, N% 13.20; Found: C% 56.41, H% 7.54, N% 13.31.

EXAMPLE 3 Methyl ether of 1-n-propyloxycarbonyl-1,2,5,6-tetrahydropyridin-3-carboxaldehyde oxime

To a solution of 1.5 g of 1,2,5,6-tetrahyropyridin-3-carboxaldehyde-O-methyloxime dissolved in 60 cm³ of benzene, 1.5 cm³ of triethylamine is added and while maintaining the temperature between 5° and 10° C., 1.23 cm³ of propyl chloroformate is added slowly. After 30 minutes at ambient temperature, and washing with 20 cm³ of 1N hydrochloric acid and then with water, the solvent is evaporated off under reduced pressure, and the residue is distilled at 170° C. under 0.07 mbar. 2.3 g of the expected product is obtained.

Analysis: C₁₁ H₈ N₂ O₃. Calculated: C% 58.39, H% 8.02, N% 12.38; Found: C% 58.12, H% 8.06, N% 12.12.

EXAMPLE 4 Methyl ether of 1-allyloxycarbonyl-1,2,5,6-tetrahydropyridin-3-carboxaldehyde oxime

To a solution of 1,2,5,6-tetrahydropyridin-3-carboxaldehyde-O-methyloxime in 40 cm³ of benzene, 1.5 cm³ of triethylamine and 1.17 cm³ of 2-propenyl chloroformate are added. The mixture is agitated for 30 minutes at ambient temperature, then treated with 20 cm³ of 5% hydrochloric acid, then twice with 20 cm³ of water. The solvent is evaporated off, then the residue is distilled at 200° C. under 0.08 mbar. 2.25 g of the expected product is obtained.

Analysis: C₁₁ H₁₆ N₂ O₃ Calculated: C% 58.91, H% 7.19, N% 12.49; Found: C% 58.96, H% 7.25, N% 12.41.

EXAMPLE 5 Methyl ether of 1-benzyloxycarbonyl-1,2,5,6-tetrahydropyridin-3-carboxaldehyde oxime Method A

To a solution of 8 g of 1-benzyl-1,2,5,6-tetrahydropyridin-3-carboxaldehyde-O-methyl oxime in 100 cm³ of benzene, there is added 23 cm³ of benzyl chloroformate at 50% in toluene, and the whole is taken to boiling point for 4 hours, then cooled, washed with 2N hydrochloric acid and then with water. The solvent is evaporated off under reduced pressure, then the residue is distilled at 200° C. under. 0.05 mbar. 4.1 g of the expected product is obtained.

Method B

To a solution of 1.5 g of 1,2,5,6-tetrahydropyridin-3-carboxaldehyde-O-methyl oxime in 20 cm³ of benzene, and B 1,08 g of triethylamine, there is added 3,4 cm 3 of benzylchloroformate at 50% in toluene, and the whole is agitated for one hour at ambient temperature, washed with 2N hydrochloric acid and with water. The solvent is evaporated off under reduced pressure, then the residue is distilled at 230° C. under 0.06 mbar. 2.1 g of the expected product is obtained.

Analysis: C₁₄ H₁₆ N₂ O₃ Calculated: C% 65.54, H% 6.72, N% 10.14; Found: C% 65.68, H% 6.61, N% 10.21.

EXAMPLE 6 Methyl ether of 1-phenyloxycarbonyl-1,2,5,6-tetrahydropyridin-3-carboxaldehyde oxime Method A

To a solution of 3.3 g of 1-methyl-1,2,5,6-tetrahydropyridin-3-carboxaldehyde-O-methyloxime, prepared as indicated in the patent application EP 239445, in 30 cm³ of dichlorethane, 4.5 g of phenyl chloroformate is added, and the whole is heated for 3 hours to reflux. The insoluble matter (hydrochloride of the starting product) is filtered off, then the remainder is evaporated to dryness under reduced pressure. The residue is chromatographed on silica (eluent: benzene-ethyl acetate 8-2). 4 g of the expected product is obtained after distilling at 220° C. under 0.06 mbar.

Method B

To a solution of 3 g of 1-ethyl-1,2,5,6-tetrahydropyridin-3-carboxaldehyde-O-methyloxime, prepared as indicated in the patent application EP 239445, in 30 cm³ of dichloroethane, 4.7 cm³ of phenyl chloroformate is added. The whole is taken to reflux for 3 hours, treated with 20 cm³ of 5% hydrochloric acid, then twice with 20 cm³ of water. The solvent is evaporated off, then the remainder is taken up with diethyl ether, the insoluble matter is filtered off, and the filtrate is evaporated to dryness. The residual oil is distilled at 210° C. under 0.03 mbar, so obtaining 2.18 g of the expected product

Analysis: C₁₄ H₁₆ N₂ O₃ Calculated: C% 64.6, H% 6.20, N% 10.76; Found: C% 64.72, H% 6.35, N% 10.65.

EXAMPLE 7 Methyl ether of [1-(2-methylsulphonyl)ethoxy-carbonyl]1,2,5,6-tetrahydropyridin-3-carboxaldehyde oxime

To a solution of 1.5 g of 1,2,5,6-tetrahydropyridin-3-carboxaldehyde-O-methyloxime in 40 cm³ of anhydrous benzene and 1.5 cm³ of triethylamine cooled to 5° C., 3.1 g of (2-methylsulphonyl)ethyl-4-nitrophenyl carbonate is added. The reaction is continued for 1 hour at ambient temperature, then the organic phase is washed with water and evaporated to dryness under reduced pressure. The residue is chromatographed on silica (eluent: ethyl acetate), and 1.6 g of the expected product is obtained, crystallized from benzene. m.p. 93°-94° C.

Analysis: C₁₁ H₁₈ N₂ O₅ S Calculated: C% 45.50 H% 6.25, N% 9.65; Found: C% 45.63, H% 6.29, N% 9.61.

EXAMPLE 8 Methyl ether of 1-adamantyloxycarbonyl-1,2,5,6-tetrahydropyridin-3-carboxaldehyde oxime

To a solution of 1.5 g of 1,2,5,6-tetrahydropyridin-3-carboxaldehyde-O-methyloxime in 40 cm³ of benzene and 1.5 cm³ of triethylamine, 2.13 g of adamantyl fluoroformate is added at 5° C. After 15 minutes at ambient temperature, washing with 2N hydrochloric acid and then with water, evaporating to dryness under reduced pressure and crystallizing from hexane, 2.6 g of the expected product is obtained. m.p. 105°-106° C.

Analysis: C₁₈ H₂₆ N₂ O₃ Calculated: C% 67.90, H% 8.23, N% 8.80; Found: C% 68.02, H% 8.28, N% 8.76.

EXAMPLE 9 Methyl ether of 1-isopropyloxycarbonyl-1,2,5,6-tetrahydropyridin-3-carboxaldehyde oxime

To a mixture of 1.4 g of 1,2,5,6-tetrahydropyridin-3-carboxaldehyde-O-methyloxime and 1.01 g of anhydrous triethylamine in 30 cm³ of benzene, 1.22 g of isopropyl chloroformate in solution in benzene is added at 10° C. After agitating for 30 minutes at ambient temperature, decanting, washing the organic phase, evaporating to dryness and chromatographing the residue on silica (eluent: toluene-ethyl acetate, 8-2), a residue is obtained which is distilled at 180° C. under 0.08 mbar. 1.35 g of the expected product is obtained, m.p. 40°-41° C.

Analysis: C₁₁ H₁₈ N₂ O₃ Calculated: C% 58.39, H% 8.02, N% 12.38; Found: C% 58.19, H% 8.13, N% 12.54.

EXAMPLE 10 Methyl ether of 1-butyloxycarbonyl 1,2,5,6-tetrahydropyridin-3-carboxaldehyde oxime

To a solution of 1.5 g of 1,2,5,6-tetrahydropyridin-3-carboxaldehyde-O-methyloxime in 20 cm³ of benzene and 1.2 g of triethylamine, 1.46 g of butyl chloroformate is added at 10° C. After agitating for 2 hours at ambient temperature, washing with 2N hydrochloric acid, then evaporating to dryness and distilling the residue at 220° C. under 0.08 mbar, 1.85 g of the expected product is obtained.

Analysis: C₁₂ H₂₀ N₂ O₃ Calculated: C% 59.98, H% 8.39, N% 11.66; Found: C% 59.72, H% 8.49, N% 11.77.

EXAMPLE 11 Methyl ether of 1-[2-(phenyl)-ethyloxy]-carbonyl-1,2,5,6-tetrahydropyridin-3-carboxaldehyde oxime

To a mixture of 1.4 g of 1,2,5,6-tetrahydropyridin-3-carboxaldehyde-O-methyloxime and 1.01 g of triethylamine in 40 cm³ of benzene, 1.85 g of [(2-phenyl)ethyl]chloroformate is added at +10° C. After 30 minutes at ambient temperature, washing with dilute hydrochloric acid, then evaporating to dryness, the residue is purified by chromatography of alumina (eluent: cyclohexane-ethyl acetate 9-1), then distilled under 0.07 mbar at 250° C. 2.2 g of the expected product is obtained.

Analysis: C₁₆ H₂₀ N₂ O₃ Calculated: C% 66.65, H% 6.99, N% 9.72; Found: C% 66.51, H% 7.10, N% 9.79.

EXAMPLE 12 Methyl ether of 1-parachlorophenyloxy-carbonyl-1,2,5,6-tetrahydropyridin-3-carboxaldehyde oxime

To a mixture of 1.4 g of 1,2,5,6-tetrahydropyridin-3-carboxaldehyde-O-methyloxime and 1.01 g of triethylamine in 40 cm³ of benzene, 1.91 g of p-chlorophenyl chloroformate (J. Am. Chem. Soc. 47, 2607) is added at +10° C. in 30 cm³ of benzene. After 3 hours at ambient temperature, washing with dilute hydrochloric acid, then evaporating to dryness, the residue is purified by chromatography on alumina (eluent: cyclohexane-ethyl acetate 7-3). 1.9 g of the expected product is obtained, crystallized from cyclohexane. m.p. 96°-98° C.

Analysis: C₁₄ H₁₅ N₂ O₃ Calculated: C% 57.05, H% 5.13, N% 9.51; Found: C% 56.78, H% 4.97, N% 9.37.

EXAMPLE 13 Methyl ether of 1-p-isopropylphenyloxycarbonyl-1,2,5,6-tetrahydropyridin-3-carboxaldehyde oxime

To 1.4 g of 1,2,5,6-tetrahydropyridin-3-carboxaldehyde-O-methyloxime in 40 cm³ of benzene and 1.01 g of triethylamine, 1.99 g of p-isopropylphenyl chloroformate (Brit. Pat. 798 659 (1978)) is added at 10° C. in solution in 20 cm³ of benzene. After 1 night at ambient temperature, washing with dilute hydrochloric acid, then evaporating to dryness, the residue is purified by chromatography on alumina (eluent: cyclohexane-ethyl acetate 9-1). After crystallizing from cyclohexane, 2 g of the expected product is obtained. m.p. 100°-102° C.

Analysis: C₁₇ H₂₂ N₂ O₃ Calculated: C% 67.53, H% 7.33, N% 9.27; Found: C% 67.70, H% 7.33, N% 9.27; Found: C% 67.70, H% 7.44, N% 9.14.

EXAMPLE 14 Methyl ether of 1-(3,4-dimethoxyphenyloxy-carbonyl-1,2,5,6-tetrahydropyridin-3-carboxaldehyde oxime

To a solution of 1.2 g of 1,2,5,6-tetrahydropyridin-3-carboxaldehyde-O-methyloxime in 20 cm³ of benzene and 1.2 cm³ of triethylamine, 1.86 g of 3,4-dimethoxyphenyl chloroformate is added, with agitation for 45 minutes, then washing with 10% hydrochloric acid and evaporating to dryness. The residue is chromatographed on alumina (eluent: cyclohexane-ethyl acetate 7-3). 1.85 g of the expected product is obtained, crystallized from cyclohexane. m.p. 143°-145° C.

Analysis: C₁₆ H₂₀ N₂ O₅ Calculated: C% 59.99, H% 6.29, N% 8.75; Found: C% 60.24, H% 6.21, N% 8.61.

EXAMPLE 15 2-propynyl ether of 1-ethyloxycarbonyl-1,2,5,6-tetrahydropyridin-3-carboxaldehyde oxime

To a solution of 1,2,5,6-tetrahydropyridin-3-carboxaldehyde-O-(2-propynyl)oxime, prepared as indicated in patent application EP 239,445, in 50 cm³ of of benzene, 1.42 cm³ of triethylamine and 1.02 cm³ of 95% ethylchloroformate are added at 5° C., with agitation for 30 minutes, then washing with water and evaporating to dryness under reduced pressure. The residue is purified by chromatography on alumina (eluent: benzene-diethyl ether, 1-1), then evaporated to dryness, taken up with benzene, treated with sodium sulphate and active carbon, filtered, and taken to dryness under reduced pressure. 1.95 g of the expected product is obtained, m.p. 55° C.

Analysis: C₁₂ H₁₆ N₂ O₃ Calculated: C% 61.00, H% 6.83, N% 11.86; Found: C% 61.23, H% 6.66, N% 11.71.

EXAMPLE 16 Methyl ether of 1-tertbutyloxycarbonyl-1,2,5,6-tetrahydropyridin-3-carboxaldehyde oxime

To a solution of 1.5 g of 1,2,5,6-tetrahydropyridin-3-carboxaldehyde-O-methyloxime in 40 cm³ of benzene, 1.5 cm³ of triethylamine is added, the mixture is cooled to 5° C. and 2.33 g of tertbutyl carbonate is added. After 10 minutes at ambient temperature, washing with 2N hydrochloric acid and then with water, evaporating under reduced pressure, then isolating the product by distilling at 150° C. under 0.07 mbar, 2.2 g of the expected product is obtained.

Analysis: C₁₂ H₂₀ N₂ O₃ Calculated: C% 59.83, H% 8.5, N% 11.49; Found: C% 60.00, H% 8.39, N% 11.66.

EXAMPLE 17 Methyl ether of 1-(2-trimethylsilylethyloxy)carbonyl-1,2,5,6-tetrahydropyridin-3-carboxaldehyde oxime

To a solution of 1.5 g of 1,2,5,6-tetrahydropyridin-3-carboxaldehyde-O-methyloxime in 40 cm³ of benzene and 1.5 cm³ of triethylamine, 3.03 g of paranitrophenyl carbonate of (2-trimethylsilyl)ethyl is added, at 5° C., with agitation for 3 hours at ambient temperature, then washing with water and evaporating under vacuum. After purifying by chromatographing on silica (eluent: benzene-diethyl ether 1-1), the expected product is isolated by distilling at 220° C. under 0.08 mbar. 2.3 g of the expected product is obtained.

Analysis: C₁₃ H₂₄ N₂ O₃ Si. Calculated: C% 54.89, H% 8.50, N% 9.85; Found: C% 54.85, H% 8.59, N% 9.76.

Example of pharmaceutical compositions

(a) Tablets have been prepared answering to the following formula:

Product of example 12 . . . 50 mg

Excipient q.s. for a tablet finished at . . . 300 mg

(detail of excipient: lactose, corn starch, treated starch, rice starch, magnesium stearate, talc).

(b) Capsules have been prepared answering to the following formula:

Product of example 12 . . . 60 mg

Excipient q.s. for a capsule finished at . . . 300 mg

(detail of excipient: talc, magnesium stearate, aerosil).

PHARMACOLOGICAL STUDY Acute toxicity

The test was carried out on male mice (CD₁ Charles Rivers), of 22 to 24 g, without food for 16 hours. The products are administered by oral route at doses of 1000, 500, 250, 125, and 62 mg/kg. The mortality is noted during the 7 days following the treatment. The results are shown in Table 1.

                  TABLE 1                                                          ______________________________________                                         Example        LD.sub.50 mg/kg                                                 ______________________________________                                         2              175                                                             4              175                                                             6              >500                                                            13             >1000                                                           12             >1000                                                           14             175                                                             Arecoline HBr  600                                                             ______________________________________                                    

Test of ileum isolated from guinea-pig

Pieces of ileum are removed from guinea-pigs killed by decapitation. The isolated ileum is placed in 10 cm³ of Tyrode solution at 37° C. and aerated with a mixture of oxygen (95%) and carbon dioxide gas (5%). The contractions due to the products are registered by means of a detector connected to a polygraph. The products to be tested are added at concentrations between 1.10⁻³ M and 1.10⁻⁸ M/l.

The products presenting a contracting effect are tested vis-a-vis atropine and hexamethonium in order to establish if the activity is of "muscarine" of "nicotine" type.

The possible antagonist activity of the products is tested vis-a-vis acetylcholine.

The agonist activity is expressed in pD₂ (negative logarithm of the dose which produces 50% of the maximum effect).

The antagonist activity is expressed in DE₅₀ (dose reducing by 50% the maximum response induced by acetylcholine). The results are shown in Table 2.

                  TABLE 2                                                          ______________________________________                                         Example        pD.sub.2                                                                              DE.sub.50 mg/kg                                          ______________________________________                                                               --                                                       2              4.47   --                                                       4              <4      6.0 × 10.sup.-4                                   6              <3     >1 × 10.sup.-3                                     13             <4     >1 × 10.sup.-4                                     12             <4     >1 × 10.sup.-4                                     14             <4     >1 × 10.sup.-4                                     arecoline      6.48   --                                                       ______________________________________                                    

Diarrhoeic activity

The test is carried out on male mice (CD₁ Charles Rivers) weighing 25 to 30 g, which have fasted for 6 hours. The product dissolved at 5% in methocel is administered by oral route by means of an oesophage probe.

Control animals receive only the excipient.

After treatment, the animals are placed separately in cages of which the base is covered with blotting paper, and they are put under observation for 30, 60, 120 and 180 minutes.

The sheets of absorbent paper are changed after each observation.

The consistency of the feces is evaluated according to the method of Randall and Baruth (Arch. Int. Pharmacodyn. 220, 94, 1976) according to the following scale of values.

0: consistency firm,

1: feces slightly soft, with or without a damp halo,

2: feces slightly soft, with a well-defined circle of humidity,

3: feces soft with a large circle of humidity,

4: feces without consistency with a very large circle of humidity.

For each product, the dose is noted which causes diarrhoea in 50% of the animals according to the method of Miller and Tainter (Proc. Soc. Exp. Biol. Med., 57, 261, 1944). The results are shown in Table 3.

                  TABLE 3                                                          ______________________________________                                         Example      DE.sub.50 mg/kg                                                   ______________________________________                                         2            25                                                                4            3                                                                 6            100                                                               13           >50                                                               12           >50                                                               14           >50                                                               arecoline    35                                                                ______________________________________                                    

Hypothermic activity

The test is carried out on male mice (CD₁ Charles Rivers) weighing 25-30 g, which have fasted for 6 hours.

The temperature of the body is noted by means of a thermocouple inserted about 1.5 cm in the rectum and connected to an electric temperature recorder.

The products are administered by oral or sub-cutaneous route and the temperatures are noted at the instant 0 and at 30 minutes, 1 hour, 2 hours and 2-and-a-half hours after treatment.

The degree of hypothermia is evaluated as the difference between the treated animals and the controls, and the dose necessary to reduce the body temperature by 1° C. is noted. The results are shown in Table 4.

                  TABLE 4                                                          ______________________________________                                                   Effective dose (-1° C.) in mg/kg                              Example     O.R.        SC.R                                                   ______________________________________                                         2           3.9         3.6                                                    4           1.6         1.8                                                    6           4.6         2.3                                                    13          3.4         8.8                                                    12          2.2         2.9                                                    14          0.7         0.7                                                    arecoline   194         3.0                                                    ______________________________________                                    

Variation of the body temperature

The duration of action of the products is determined, using the doses able to reduce the temperature by 1° to 1.5° C. See Table 5.

                                      TABLE 5                                      __________________________________________________________________________     Variations of the body temperature (°C.)                                Dose              Treatment Time in Minutes                                    Example                                                                              mg/kg                                                                              Administration                                                                         0   30  60  120 180                                          __________________________________________________________________________     2     5.  os      +0.2                                                                               -1.2**                                                                             -1.1**                                                                             -0.1                                                                               ±0.                                             5.  sc      +0.2                                                                               -1.5**                                                                             -1.4**                                                                             -0.1                                                                               ±0.                                       4     2.  os      -0.1                                                                               -1.2**                                                                             -1.1**                                                                             -0.1                                                                               -0.1                                               2.  sc      -0.1                                                                               -0.9**                                                                             -0.1**                                                                             -0.2                                                                               -0.1                                         6     7.5 os      -0.1                                                                               -1.1**                                                                             -1.6**                                                                             -0.6**                                                                             ±0.                                             3.5 sc      -0.1                                                                               -0.6**                                                                             -1.4**                                                                             -0.9**                                                                             0.1                                          13    6.25                                                                               os      +0.2                                                                               -0.4**                                                                             -1.6**                                                                             -0.4**                                                                             -0.1                                               12.5                                                                               sc      +0.2                                                                               ±0.                                                                             -0.7**                                                                             -1.4**                                                                             -1.1**                                       12    3.12                                                                               os      +0.1                                                                               -0.9**                                                                             -1.4**                                                                             -0.3*                                                                              ±0.                                             3.12                                                                               sc      -0.1                                                                               -0.1                                                                               -1.1**                                                                             -1.2**                                                                             -0.5**                                       14    1.  os      +0.1                                                                               -1.1**                                                                             -1.4**                                                                             -0.2                                                                               +0.1                                               1.  sc      +0.2                                                                               -0.7**                                                                             -1.3**                                                                             -0.5**                                                                             ±0.                                       Arecoline,                                                                           200 os      +0.1                                                                               -1.1**                                                                             -1.0**                                                                             -0.2                                                                               -0.1                                         HBr   3.5 sc      -0.1                                                                               -1.5**                                                                             -0.1                                                                               +0.2                                                                               +0.2                                         __________________________________________________________________________      **Values differing from the controls in a significant manner (p < 0.05);       *(p < 0.01)                                                               

What is claimed is:
 1. A compound of the formula (I): ##STR10## in which R' represents hydrogen, a linear, branched or cyclic alkyl, alkenyl or alkynyl, containing up to 8 carbon atoms, and R represents a linear, branched or cyclic alkyl unsubstituted or substituted by alkylsulphonyl containing up to 18 carbon atoms or the radical Si--Alk₃ wherein Alk represents alkyl containing up to 4 carbon atoms, alkenyl or alkynyl, containing up to 18 carbon atoms, aryl containing up to 14 carbon atoms, unsubstituted or substituted by one or more of halogen, linear or branched alkyl or linear or branched alkoxy, aralkyl containing up to 18 carbon atoms, unsubstituted or substituted by one or more of halogen, linear or branched alkyl or linear or branched alkoxy, or an addition salt with an organic or a mineral acid thereof.
 2. The compound of the formula (I) as defined in claim 1, in which R' represents a linear alkyl, alkenyl or alkynyl, containing up to 4 carbon atoms, or an addition salt with an organic or a mineral acid thereof.
 3. The compound as defined in claim 2, in which R' represents methyl, or an addition salt with an organic or a mineral acid thereof.
 4. The compound as defined in any one of claims 1 to 3, in which R represents a linear alkyl, alkenyl or alkynyl containing up to 4 carbon atoms, or an addition salt with an organic or a mineral acid thereof.
 5. The compound as defined in claim 4, in which R represents ethyl, or an addition salt with an organic or a mineral acid thereof.
 6. The compound as defined in claim 4, in which R represents allyl, or an addition salt with an organic or a mineral acid thereof.
 7. The compound as defined in any one of claims 1 to 3, in which R represents phenyl, or an addition salt with an organic or a mineral acid thereof.
 8. The compound as defined in any one of claims 1 to 3, in which R represents substituted phenyl, or an addition salt with an organic or a mineral acid thereof.
 9. The compound as defined in any one of claims 1 to 3, in which R represents 4-chlorophenyl, or an addition salt with an organic or a mineral acid thereof.
 10. The compound as defined in any one of claims 1 to 3, in which R represents 4-isopropylphenyl, or an addition salt with an organic or a mineral acid thereof.
 11. The compound as defined in any one of claims 1 to 3, in which R represents 3,4-dimethoxyphenyl, or an addition salt with an organic or a mineral acid thereof.
 12. Methyl-ether of 4-chlorophenyloxycarbonyl-1,2,5,6-tetrahydropyridin-3-carboxaldehyde oxime as well as its addition salt with an organic or a mineral acid thereof.
 13. A therapeutic composition for the treatment of patients suffering from senile dementia, Alzheimer's disease or memory defects, comprising a cholinergically effective amount of a compound as defined in claim 1 and a pharmaceutically acceptable carrier.
 14. A method of treating patients suffering from senile dementia, Alzheimer's disease, or memory defects, comprising administering to the patient a cholinergically effective amount of a compound as defined in claim
 1. 